A show airing Wednesday night on TLC follows a television star whose search of her family history appears to have turned up one of the Missouri State Penitentiary’s many dark stories.

TV star Cynthia Nixon walks along the inside of A-Hall, the oldest of the buildings still standing at Missouri State Penitentiary. (screenshot from TLC show preview)

Cynthia Nixon is perhaps best known for her role as Miranda Hobbes on the show Sex and the City. She is featured on the season premier of TLC’s “Who Do You Think You Are?” Wednesday night, in which she traces her father’s family history.

“She connects to a courageous woman who suffered terribly, but never gave up,” says the TLC preview video for the episode.

State Archivist John Dougan participated in that research, using Missouri’s State Archives.

“We provided a number of documents,” says Dougan.

That search took her to MSP where her great-great-great grandmother was to have served time in the 1840s, but there was a problem.

“The prison at that time was not built for women inmates,” says Dougan.

Dougan can’t say exactly what was discovered so it won’t spoil the show, and it’s not easy to guess why anyone might have been sent to prison in the 1840s. By today’s standards, some people who were convicted then, wouldn’t be.

“It’s a very interesting story and really it ties to whether or not did she belong in the prison,” says Dougan.

While Dougan can’t confirm who Nixon’s ancestor was, one name in the show’s video preview is Martha Casto. Some of her story is known.

According to one source, Casto was sentenced to five years for murder in August, 1843. Because the prison had no facilities for women, she was assigned to work as a domestic servant in the homes of businessmen leasing the prison.

This screenshot from the TLC preview for “Who Do You Think You Are?” shows part of a document mentioning Martha Casto, a figure in MSP’s history.

While there, Casto became pregnant and was mistreated by the wife of one of the lessees. She ran away but was soon captured by prison officials and placed in solitary confinement. Eventually she gave birth in the prison with the help of a male convict and both mother and child remained imprisoned until she was pardoned in December, 1844, partly out of concern for the child’s health in an unheated prison cell during winter.

Whether Casto and her child are related to Nixon or not, hers is just one of the stories of what women faced at the state prison, particularly in its early decades of operation.

Not all family backgrounds might be as dramatic as Nixon’s, but Dougan says the state archives offer a great deal of information that can help turn them up.

“I think that the “Who Do You Think You Are?” television show, what it really shows is the kind of records, the diversity of records, that you can find researching at the Missouri State Archives or other local archives or on our website at Missouri Digital Heritage dot com,” says Dougan. “It shows the same kind of things that everyone can find on their family whether it’s census records, marriage records or any other kind of record that they might have, or prison records.”

Find out who Nixon’s ancestor is and what the connection to Missouri State Penitentiary is when the new season of “Who Do You Think You Are?” premiers Wednesday night on TLC.